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ELECTROLYTIC PROCESS.

No Drawing.

To all whom it may concern Be it known that I, KENNETH S. GUrrER- MAN, a citizen of the United States, and resident of New York city, in the county of New York and State of New York, have invented certain new and useful Improvements in Electrolytic Processes, of which the following is a specification.

My invention relates in general to an electrolytic process for scouring the electrodes from electrolytic cells of their by-products deposits and specifically relates to such a process incidental to the precipitation of cobalt oxids by electrolysis from solutions containing soluble salts of cobalt. While the process is applicable to the securing of metal deposits of any character from electrodes, the refinements of the process have been worked out experimentally and practically in connection with the electrodes used in the electrolytic precipitation of cobalt oxid and the invention will be particularly described with reference to such electrodes.

One process at present ractised for form-- ing the oxid or hydrate oxid of cobalt is to provide an electrolytic cell using plates, usually formed of a graphitic composition, for the electrodes and a solution of a soluble salt of cobalt, such as the sulfate or chlorid, as the electrolyte. Under certain conditions, as when the electrolyte is neutral or prefer ably having a very weak acidity, electric current passed through the cell will cause an oxid of cobalt to form at the anode plate, usually at a relatively rapidrate and, more slowly, will cause a metallic deposit to form as a coating on the cathode plate. This deposit contains metallic cobalt but the composition of the deposit naturally varies with the character of the electrolyte.

While the formation of this metallic coating is slow, yet it is accumulative and eventually the amount of coating becomes a serious drawback to the economical utilization of the process dueto the amount of metal withdrawn from the oxid forming process. It is, of course, possible to strip the deposit from the cathode plate but such a procedure requires time, the plates are frequently broken and in general, any stripping process is expensive and otherwise unsatisfactory.

One of the objects of the invention is to provide a simple. positive, inex ensive and conveniently controlled means ftir preventing the accumulation of metallic deposition on the electrode plate in an electrolytic cell.

Specification of Letters Patent.

Patented Sept. 2, 1919.

Application filed February 2, 1916. Serial No. 75,658.

Another object of the invention is to discharge the electrode plates of their deposit with the least possible interruption to the electrolytic process and incidentally to obtain the deposit in a readily soluble form convenient for use to enrich the electrolyte.

I attain these objects broadly by taking the metal coated cathode plates obtained from a metal depositing electrolytic cell and using them as anode plates in an electrolytic cell having an electrolyte with an acidity sufficient to prevent the redepositing of the mgfal when current is passed through the ce The changing of the polarity of the electrodes under these conditions gives rise to a reducing action in the said electrolyte cell, and causes the metallic coating to act as a soluble anode until all of the metallic deposits are dissolved in the acid electrolyte, tlms'returning the deposit to the solution and effectively cleaning the electrode plates.

When the electrode cleaning process is practised in connection with a cobalt oxid forming process in which fresh electrolyte is added to the solution from which the cobalt oxid has been withdrawn and when it is desired to clean the electrodes, it is usual to acidity an incoming batch of the solublecobalt-salt-eleetrolyte slightly so that it may have an acidity of a strength to prevent the redeposition of the metal dissolved from the cathode electrode. The acidity is attained by adding a mineral acid, preferably sulfuric acid and not less than twenty grams of free acid to each liter of the electrolyte which is in contact with the electrodes. This acidifying of electrolyte acts to prevent the concurrent deposition of the more cathode plates. The electric current is passed. through the cell in a direction so that the coated plates which were cathode plates during the cobalt oxid forming process are anode plates during the deposit dissolving process. This reversal of current may be attained by means of a suitable switch con trolling the direction of the current through the cell or under some conditions, itmay be preferable to bodily remove the coated plates to a different cell particularly designed to be used in the plate scouring process.

In the case where the same cell is used for both processes. it is necessary after the metal coating is entirely dissolved, and it is desired to proceed with the cobalt oxid forming process only to restore theelectrolyte to its normal neutral or very slightly acid condition.

This is attained by neutralizing any acid present preferably by supplying soda in so lution to the bath in quantities Just suflicient to counteract any free acid present or ratherto leave the solution weakly acid, possibly one or two grams of acid to the liter.

As the coating is dissolved rapidly there is but little interruption to the cobalt oxid forming process and the metal cobalt is returned to the electrolyte thus savingmetal which might otherwise belost. Further, the metal is returned to the electrolyte in a soluble state ready. to be converted into its oxids and acting to enrich the electrolyte temporarily.

Relatively little current is consumed during the deposit dissolving process, so that.

the process is economical not only in the retention of the deposited metal, and in the short interruption to the cobalt oxid forming process but also due to the low current consumption. 1

It is noted that this is not a plating process, but on the contrary is. for the purpose of dissolving plate and returning the metal into solution.

Having thus described my invention, I claim 1. In the art of cleaning electrodes coated with metal cobalt deposits, the rocess which consists in assembling one, 0 said coated electrodes in;; an electrolytic cell provided with an electrolyte having an acidity at least equal to that obtained by adding twenty.

grams of free sulfuric acid to each liter of electrolyte and passing the current throu h saidcell utilizing the coated electrode as t e anode of the cell.

2. In the art of electrolytically producing cobalt oxids, the process which consists in passing a current through an electrolytic cell having a neutral or substantially neutral electrolyte containing a soluble cobalt salt thus causing the formation of a deposit on the cathode plate, introducing a new charge of electrolyte, acidifying the new charge of electrolyte, passing the current in a direction reversed from its original direction through the .cell until any metal deposited on the original cathode electrode is dissolved and then restoringthe cell to its original electrical and neutral condition.

3. In the. art of cleaning cathode elec-v trodes of their coating of metallic deposits, the process which consists 1n assembling one of such metal-coated electrodes in an elecdissolved from the cathode electrode and passing an electric current through the cell and in a direction to cause the metallic deposit on the electrode to constitute a soluble anode.

4. In the art of cleaning electrodes which have a metal cobalt deposit thereon, the process which consists in assembling one of such electrodes in an electrolytic cell containing an acid electrolyte and passing an electric current through the cell and in-a direction to cause said coated electrode to act as the anode element of the cell.

5. The process of electrolysis which con 75 sists in first using an electrode as the oathode element of an electrolytic cell ina neutral or slightly acid electrolyte and then using said electrode as the anode element in a positively acid electrolyte whereby deposits formed on the electrode during the electrolysis with the neutral or substantially neutral electrolyte are dissolved in the acid electrolyte, the acidity being of a strength to prevent the formation of a deposit on the cathode electrode of the cell during the dissolving action.

f 6. In the art of dissolving the metallic deposit on an electrode which has constituted the cathode plate in an electrolytic cell, the process which consists in assembling such electrode as the anode element in an electrolytic cell having an .solve metal in solution.

7; In the art of cleaning a cathode plate having an electrolytic metallic deposit thereon, the process which consists in assembling said electrode having'the deposit thereon in an electrolytic cell containing a deposit dissolving electrolyte designed to prevent the redeposition of the electrode deposit and using said deposit carrying electrode as the anode electrode of such cell.

8. In the art of cleaning a cathode plate 7 having an electrolytic metallic deposit thereon, the process which consists in assembling said metal coated electrode in an electrolytic cell containing an electrolyte capable of dissolving the metal on the electrode and capable of preventing its redeposition and passing an electriccurrent through said cell and in a direction to cause said coated electrode to act as an anode element of the cell.

Signed at New York city in the county of, New York, and State of New York this twenty-fourth day of January, A. D. 1916.

KENNETH S. GUITERMAN. 

